1. Field of the Invention
The present invention relates to a loading device for a tire assembly drum wherein a cord strip intended for the belt or body is removed from a storage roll, separated from a backing strip and supplied by means of guide devices to the surface of a tire assembly drum, forming at least one compensating loop in the process.
2. Description of the Prior Art
Loading devices are known wherein the cord strip is removed from a storage roll, stored in the interim in the form of a long compensating loop and then mounted on the tire assembly drum via extensible and retractable guide elements. The compensating loop is designed to counterbalance the reciprocating movement of the guide elements. Specific heavy parts such as steel threads are held in the cord strip by means of a material having a lower yield point such as non-vulcanized rubber. As a result, this cord strip is extremely susceptible to distortion. It can only bear minimal loads transversally of the thread direction. Distortion can even be produced by the inherent weight of the steel cord in the compensating loop. A distorted cord strip causes irregularity of the finished tire and possible rejection of the same. For this reason, the cord strip is generally only supplied indirectly via the backing strip which is designed to prevent sticking of the cord strip on the storage roll.
A disadvantage of this known loading device is that the drive for its individual elements is provided by the shaft of the tire assembly drum, for example, via chain drive systems. These chain drive systems are very long and block the passage between the loading device and the tire assembly drum. Even a slight amount of slack in the chain causes distortion of the cord strip. When the dimensions of the tire assembly drum are varied the operating rate of the individual devices must also be adapted to the different peripheral speed of the drum.
Loading devices are also known wherein the individual devices and the tire assembly drum are driven by separate synchronized direct current motors. However, with continuous cord strip consumption the relationship of the diameter of gyration between the tire assembly drum and the supply roll of the loading device tends to vary. This impedes regular acceleration and deceleration of the individual cooperating elements. The same problems occur when the dimensions of the tire assembly drum are varied.
Another known type of loading device employs an independent rotary current drive for the tire assembly drum and feed rollers. Large cord compensating loops are provided between the individual stations. The elements of the loading device fill the compensating loops associated therewith independently of a straight drum offtake. The tire assembly drum removes the steel cord hanging in this loop independently of the cord strip storage roll. To avoid stresses in the cord strip the unwinding rate must be greater than the circumferential speed of the largest tire assembly drum incorporated in this tire assembly machine. However, if the compensating loops are too large, distortion of the cord strip is frequently produced as a result of its own considerable weight. The compensating loop sags markedly during operating passes in which the tire assembly drum does not withdraw any cord strip. When the compensating loops are long more kinks will be needed in the material and, as a result, the cord strip is again distorted.
As the cord strip is shortened when there is an oblique thread angle at the drum, a long end is left over. In the known loading devices this end is bent back manually or by a mechanical deflecting means and stuck fast on the upper or lower side. Both methods of bending back the end damage the sensitive cord strip.